This invention relates to an easy-opening container end wall, and more specifically to an improved easy-opening end wall having a retained tab member operative to form an opening in the end wall by rupture of a tear opening such that the ruptured tear portion also remains with the container.
The ready acceptance of easy-opening containers has resulted in extended use of this type container for a substantial number of canned products, especially beverages, such as beer, soft drinks, and the like. This type of container, in the form of a can, is characterized by a lever or tab permanently joined to a tear strip, the latter being separable from the can top to provide a pouring spout. In the form heretofore used, the tab or top is ruptured along a continuous scoreline and the pull tab and tear strip are removed as a unit and normally discarded.
The convenience of easy-opening cans has created problems because of the unfortunate and indiscriminate disposal of the severed portion of the can top. For example, beach and picnic areas have an accumulation of litter in the form of tabs and tear strips which have been removed from easy-opening cans. These discarded tabs and tear strips are quite difficult to clean up because they are small and thus pass through the tines of a rake. Being made normally of aluminum, they cannot be collected by magnetic means. Nonetheless, this type of can is widely used and it is definitely advantageous to provide a solution to the problem of littering while still providing to the public the convenience of the easy-opening cans.
The numerous advantages incident to the use of easy-opening cans has given rise to an industry which has developed to the point where standard procedures and equipment are now in widespread use. For example, many of the machines now used to form the end wall of a container include five stations in which various operations are performed to provide an end unit for a container. By way of example, the first station usually forms the "bubble," transformed into a button in the second station, followed by scoring and forming the rupturable container opening in the third station. In the fourth station any embossing of logo or other information in the container end is carried out, and in the fifth station the tab is attached, i.e. staked to the end unit.
Those in the industry are aware of the need to provide convenience containers of the easy-opening type which overcome the problems of indiscriminate disposal of tabs and tear strips from an ecological standpoint. The provision of a solution to this problem, is somewhat complicated by the fact that whatever end is designed, it is desired that the end be one capable of being made on machines presently in use and which can be modified by changes of tooling in each of the stations generally used in the formation of the end wall without the need to add additional stations. If, for example, an end is designed which requires more than five separate operations, there are practical problems in bringing such an end into commerce because of the need to replace or to rebuild substantially the presently existing equipment in order to add one or more stations. Thus, any structure of an end wall which can be considered an ecology end from the standpoint of having some form of retained tab or tear strip or both and which can be made on currently existing machines with modified tooling at each of the currently existing stations has definite advantages.
Moreover, it is fairly recognized at present that standards have been established with respect to the length and diameter of the component parts and the gauge of materials used in the packaging industry, particularly the soft drink and beverage industry. Thus, in the design of a container end wall intended to form an easy opening end wall for use in the beer and beverage industry, it is desirable to maintain the dimensions of any new structure fairly within the dimensions currently in use in those respective industries.
One of the difficulties which arises in the provision of an end having substantial improvements from the standpoint of ecology is the mode of opening of the end wall. For example, the user has been accustomed to lifting the end of the tab in order to effect rupture of the tear strip. Thus, with certain types of end wall structures presently being marketed and which include push button panels, some user confusion has existed because the structure of the end wall does not include the tab. While the structure just described is intended to be opened by pushing down on the scored button to rupture the same, some users are confused by the absence of any tab or lever.
Another aspect in the provision of an easy-opening end structure which has ecological advantages is the variety of products present in the container with which the end wall is to be used. By way of example, it is known that the internal pressure in the container may vary depending upon the type of product within the container as well as the processing during packaging. For example, some beverages are packaged under considerable pressure, in some cases as much as 50 to 80 psi while other products are packaged at a somewhat lesser pressure. The packaged completed container must then be capable of withstanding substantial pressures as might be generated if the container is exposed to direct sunlight which tends to increase the internal pressure within the container. For example in some operations, the can is sealed and pasteurized resulting in the generation of internal pressure within the can.
Thus, it is definitely advantageous to be able to provide a container end structure which has wide applicability insofar as the various conditions involved in packaging the product within the container. Thus, the usual procedure is to attempt to provide a container end wall capable of withstanding the most rigorous conditions required by the industry such that a single design of end may be used over a wide variety of products. Moreover, there is the added requirement that the end structure be capable of manufacture at the usual high rates currently employed by the container industry with the equipment presently used, subject to the change of tooling necessary to adapt the presently existing multiple station machines in order to produce any new and improved end.
In summary, there are constraints within which the industry operates both from the standpoint of the standards which have been adopted, the cost of changeover and the desire to provide an end structure which is satisfactory from the standpoint of reducing the litter which has accumulated by virtue of separable tabs and tear strips.